A spinet structure lithium-nickel-manganese composite oxide attracts attention as a cathode active material for a 5 V class lithium secondary battery.
A lithium-nickel-manganese composite oxide has a superlattice structure in which nickel and manganese are regularly aligned.
As a method for producing a lithium-nickel-manganese composite oxide, a solid phase reaction method of mixing a nickel source and a manganese source and firing the mixture, or a production method using a composite hydroxide or composite oxyhydroxide containing nickel and manganese as a precursor may be mentioned. A composite hydroxide or composite oxyhydroxide containing nickel or manganese, in which metals are more uniformly distributed, is considered as a preferred precursor assuming regular alignment of nickel and manganese.
For example, as a precursor of the lithium-nickel-manganese composite oxide, a nickel-manganese composite hydroxide obtained by a coprecipitation method under an inert atmosphere has been disclosed (Patent Document 1 and Non-Patent Document 1).